Toxicological effects of chlorophenols to green algae observed at various pH and concentration of humic acid

Humic acid (HA) is ubiquitous organic matter derived by microbial metabolisms. This polymeric substance has both hydrophilic and hydrophobic moieties, and it is known that they affect to bioavailability of environmental pollutants. Objective of this study is to investigate the toxicological effects of chlorophenols to green algae observed at various pH and concentration of HA. Toxicity was determined by algal growth inhibition rate and EC₅₀ of green algae Chlorella vulgaris. As a result, toxicity of 2,4-dichlorophenol was mitigated with increase of the coexisting amount of HA and solution pH. In the case of coexisting 2.5 ppm HA, EC₅₀ of 2,4-dichlorophenol was 12.2 ppm and approximately three times higher than the case of absence of HA at pH 7.5. Meanwhile, Toxicity of 2,4,6-trichlorophenol was enhanced with increase of the coexisting amount of HA. In the case of absence of HA, EC₅₀ of 2,4,6-trichlorophenol was 13.1 ppm and approximately two times higher than the case of coexisting 2.5 ppm HA at pH 7.5. Results suggested that toxicity of chlorophenols is influenced by the electrostatic and hydrophobic interaction between HA and chlorophenols. The hypothesis of toxicity enhancement pathway was proposed in the case of equilibrium-state 2,4,6-trichlorophenol between anionic and nonionic states.

Sodium Nitroprusside Enhances Absorption in the Rat Jejunum via the Transcellular Route

It was reported that nitric oxide (NO) donors increased the permeability of water-soluble compounds across intestinal membrane with neither loss of cell viability nor release of lactate dehydrogenase. Therefore, the detail mechanism of action of NO donors on the gastrointestinal membrane has yet to be clarified. We previously reported the possibility of the enhancing effect of the NO donor on the membrane permeability via transcellular route. The purpose of this study is to clarify the mechanism of the membrane permeation-enhancing effect via the transcellular route by sodium nitroprusside (SNP), which is one of the NO donors. The effect of SNP on membrane permeation was examined by the in vitro sac method using rat jejunum. SNP increased the membrane permeation of rhodamine 123 same as using N-acetyl-L-cysteine and dithiothreitol which removes unstirred water layer (UWL). Moreover, SNP increased the membrane permeation of antipyrine and β-naphthol, which are transcellular markers. And it was also investigated the expression levels of mucins (MUCs) which are construction component of UWL and the slight change of MUCs expression by SNP was shown. It was suggested that the expression balance of MUCs is necessary to regulate transcellular permeation, and SNP may affect to UWL. This finding was considered useful for highly lipophilic drugs for which membrane permeation is restricted by the UWL.